The present invention generally relates to a method for the evaluation of noise from an axle into a vehicle and more particularly to a method for experimentally evaluating the transfer functions that dictate the amount and type of axle energy that is transferred through a vehicle suspension system into the vehicle.
Scientific evaluation of complex noise sources in automobiles, such as axles, has long been desired, particularly in view of recent advancements in the sound-proofing of modern automobiles. One problem that is encountered in this evaluation concerns the various paths through which noise may be transferred from its source into the vehicle. More specifically, the amount and type of energy that is transmitted from a noise source into the vehicle is a function of the interactions between the noise source and each item, component and/or assembly that couples the noise source to the vehicle. Without a thorough understanding and quantification of these transfer functions, the task of noise attenuation may be at least partially based upon improvements that are discovered through trial-and-error testing. Accordingly, the task of noise attenuation usually cannot be accomplished in the most expedient and efficient manner without a thorough understanding and quantification of the transfer functions that link a noise source to the vehicle.
In the context of an axle assembly, the amount and type of energy that is transmitted into the vehicle is a function of the interactions between the axle assembly and the vehicle suspension system (since the axle assembly is coupled to the vehicle suspension system) and the interactions between the vehicle suspension system and the vehicle body (since the vehicle suspension system is coupled to the vehicle body).
Mathematical (i.e., calculation-based) modeling of these transfer functions can be extremely complex and time consuming. Further complicating matters is the fact that a set of transfer functions is usually unique to a particular vehicle configuration. Changes in the suspension system, the vehicle body or the coupling of the suspension system to the vehicle body may therefore affect a vehicle""s set of transfer functions to the extent that a new mathematical model would be desired.
Accordingly, there remains a need in the art for a method which improves the speed and accuracy with which a set of transfer functions that quantify the amount and type of energy that is transmitted from an axle through a vehicle suspension system are fashioned.
In one preferred form, the present invention provides a method for evaluating energy transmission into a vehicle over at least one transfer path between an axle and a vehicle suspension system. The method includes the steps of: applying a torsional input to a gearset in the axle to torsionally excite the axle in a manner that mimics the gearset""s excitation of the axle during operation of the vehicle; and monitoring the energy that is transmitted through the vehicle suspension system into the vehicle via the at least one transfer path.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.